Originally Posted By: Arney
Was just reading this report on why the Japan quake was so large.

Apparently, current seismic understanding is that a fault typically only slips in isolated segments, but in the Japan quake, a number of different segments of the fault gave way together, resulting in the massive 9.0 quake. Sounds like that is primarily why seismologists had not predicted a larger quake (and resulting tsunami) to hit that region of Japan.

I'm curious if research like this will raise the hazard level of places like the Pacific Northwest or West Coast. That would be quite an economic cost if building codes were strengenthed for structures built in these areas.

At least among emergency planners, the magnitude of the earthquakes in Chile, New Zealand and Japan raise some new questions about our general preparedness in the PNW, although if you pore into the research questions some have been asking these question for a while, the rest of us are just starting to notice their observations. The most significant realization I think is not that a 9.0 quake could hit here, everyone assumed that, but that the 9.0 could go on for 4-5 minutes: to this point most predictions were for shorter duration quakes, a minute or so of shaking. I think that was based on research of our most recent subduction zone quake a few hundred years ago. Longer duration wuakes may have some dire consequences not considered - liquefaction would be more severe, would be far more wide spread than typically assumed, and the basic safety of built structures not as good under the longer duration shakes. There are *lots* of places I wouldn't want to be in a M9.0 5 minute quake - and depending on the timing of the quake, lots of folks will be in those places.

Whether these predictions make their way into urban planning or building code is another matter - and maybe they shouldn't. I'm not an engineer, but I'm not sure very many structures can survive a nearby 9.0M quake; or put it another way, is there a way to retrofit existing structures, most built to pre-1970s codes, to survive such a shake. Or, should we continue to build structures and infrastructures on land that will be thoroughly liquified by a quake. I think the short answer to all this is no, we build as usual, not for ultimate survival - there is far too much investment in lands and built structures subject to liquefaction to abandon it, or rebuild it to a new standard. Fundamentally, Americans have a different perspective than the Japanese - we tend to bulldoze over our historical structures (there are exceptions of course), rather than design them to survive every contingency, including an M9.0 that might occur only every 500-700 years. America has only existed for half that amount of time: we may not have enough perspective to build for a longer duration disaster cycle. So we will lose a fair amount of this build investment and the people in them should an M9.0 happen in our lifetimes. A better question may be, can we make better decisions about infrastructure, such as gas pipelines, water systems, or, say, waterfront tunnels through liquefaction zones, such that they can survive this type of quake in better shape?